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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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20th Jan 2020, 8:18 pm | #21 | |
Triode
Join Date: Jan 2020
Location: Dublin, Ireland
Posts: 10
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Re: 12" P4 Phospher CRT
Quote:
Terminal arrived in one piece. I spent the weekend cleaning it all up, keyobard disassembly, electrical contact cleaner, cleaned the PCB on both sides, checked the CAPs as best as I can. In short, it's working very well. One minor annoyance, the image seems to jitter over and back by a millimeter or so. It's not the end of the world , but if you have any clue what might be causing it, i'd love to know! |
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20th Jan 2020, 8:46 pm | #22 |
Heptode
Join Date: Mar 2014
Location: Meath, Ireland
Posts: 547
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Re: 12" P4 Phospher CRT
Could be a line sync issue, possibly caused by poor electrolytic caps. Great news that the CRT is ok.
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20th Jan 2020, 8:55 pm | #23 |
Heptode
Join Date: Aug 2009
Location: Carshalton, Surrey, UK.
Posts: 734
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Re: 12" P4 Phospher CRT
HI,
I think I had some strange problems maybe similar to the above ? and found that the switch that selects 50 or 60 hz had been set to 60hz... but changing the caps carefully might well be a good idea...
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Regards Peter B |
21st Jan 2020, 6:43 pm | #24 |
Triode
Join Date: Jan 2020
Location: Dublin, Ireland
Posts: 10
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Re: 12" P4 Phospher CRT
@linescan87 @dragonser I am using a decent 220V to 115V stepdown transformer unit. I changed the linesync DIP in the terminal switch to 50Hz and the cursor started rolling up the screen, so I assume the stepdown transformer unit changes the line frequency to 60hz, but I will check that later.
I can live with it, it's pretty minor, but I'm just curious as to how I might debug it. (I have a good scope and the full schematics for the ADM.) |
21st Jan 2020, 8:19 pm | #25 | |
Hexode
Join Date: Mar 2014
Location: Dublin, Ireland
Posts: 396
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Re: 12" P4 Phospher CRT
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Rgds John |
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22nd Jan 2020, 11:57 pm | #26 | ||
Triode
Join Date: Jan 2020
Location: Dublin, Ireland
Posts: 10
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Re: 12" P4 Phospher CRT
Quote:
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23rd Jan 2020, 5:58 am | #27 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,190
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Re: 12" P4 Phospher CRT
Most likely that DIP switch changes the digital side of things so that the vertical frequency produced by the logic board is either 50Hz or 60Hz. It won't affect the analogue circuitry on the video monitor PCB which will have to lock to that. So it may just be a matter of tweaking the vertical hold preset on that board so that the picture locks in the 50Hz setting.
That said, there is no harm in running it set to 60Hz in the UK. The only possible issues are a hum bar on the screen if the PSU is not properly smoothed (but it should be!) or a flicker between the screen display and normal electric lighting. If you don't get these problems you don't _need_ to reset the switch. |